An electric toy car with a mass of #3 kg# is powered by a motor with a voltage of #7 V# and a current supply of #1 A#. How long will it take for the toy car to accelerate from rest to #5/3 m/s#?

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Answer 1 · 2017-03-05T16:14:37

#0.6s#

Electrical power is

#P=IV#

and mechanical power is

#P = E/t#

so

#E/t = IV#

We can work out #E# by

#E = 1/2mv^2 = 1/2 xx 3 xx (5/3)^2 = 4.17J#

Rearrange the equation for time, which we want to find:

#t = E/(IV) = 4.17/(7xx1) = 0.6s#